Project 1 Lab Report - Grade: A PDF

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Project 1: Inorganic Contaminants Present in Water Sample...

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Project 1: Inorganic Contaminants Present in Water Sample Lab Report

I.

INTRODUCTION: A. Background- Determining the identity of unknown chemicals is very important and many people do it daily as their profession. By performing a variety of tests, scientists can distinguish the identity of an unknown substance. An example of this would be a Forensic Scientist collecting evidence at a crime scene. If they collect an unknown substance they can perform a series of test in the lab that can help them identify what the substance was. By determining the identity of the substance, they are adding another piece to solving a crime. Another example would be NASA trying to identify a substance on the moon or on another planet. By studying the physical and chemical characteristics they are able to simulate the processes in the lab to uncover the substances true identity. B. Theory/ Key Scientific Concepts that explain how the experiment works: 1. Precipitation Reactions- Are reactions in which a solid forms when two solutions are mixed.6 2. Solubility- When an ionic compound dissolves in water, the solutions contains its component ions. However not all ionic compounds dissolve in water. Those compounds that dissolve in water are soluble and those that don’t are insoluble.7 3. Gravimetric analysis- This analysis is based on the weights of the precipitate of a solution. In this experiment, this test is done to confirm that the final chemical selection is the unknown chemical. 4. Flame Test- This is a qualitative test based on the color of the flame when a chemical is burned. 5. pH Test- This is a quantitative test that shows us if the chemical is acidic or basic based on the pH scale. C. Hypothesis- The overall outcome of this experiment is to be able to identify an unknown chemical by comparing its chemical and physical characteristics to the characteristics of eleven other possible chemical choices. By eliminating those choices that don’t match, the chemical selection is narrowed down from eleven to three then to one final chemical.

D. Objectives1. Week 1- Perform a flame, pH, and solubility test to determine the physical and chemical characteristics of the unknown chemical. Then use the known traits to compare it to eleven other possible chemical choices and eliminating those chemicals that don’t match the unknown substance to conclude to three final choices. 2. Week 2 pt.1- Perform a flame, pH, and solubility test to determine the physical and chemical characteristics of the final three chemicals. Then use the known traits to compare it to the unknown chemical and eliminating those chemicals that don’t match the unknown substance to conclude to one final choice. 3. Week 2 pt.2- Perform a gravimetric analysis on the unknown chemical and the final chemical choice, using a precipitation reaction of each substance, to then compare precipitate masses, which can be used to confirm the identity of the unknown chemical. II.

METHODS: A. Week 1 Methods1. Acquired .5 g unknown chemical (Sample A) 2. Performed a pH test (using a pH strip and pH indicator), a flame test and a solubility test on the unknown sample to identify some characteristics that can be used to compare to the other known chemicals. 3. Researched the pH, solubility and color of the chemical when burned for all 11 possible chemical choices (which was Calcium Chloride, Sodium Nitrate, Ammonium Sulfate, Ammonium Chloride, Magnesium Sulfate, Calcium Nitrite, Sodium Acetate, Sodium Carbonate, Sodium Oxalate, and Sodium Chloride). 4. Then eliminated those chemicals that didn’t match the samples’ characteristics and narrowed down to the final three, which was Magnesium Sulfate, Ammonium Chloride, and Ammonium Sulfate. (Results from tests below under week 2)

B. Materials1. pH Test: .1 g of Unknown Sample A, 1x 50 mL beaker, distilled water, pH strips, pH indicator

2. Flame Test: Remaining amount of unknown chemical Sample A, 2x 50 mL beaker, distilled water, wire loop, Bunsen burner 3. Solubility test: .1g of Unknown Sample A, 3x 50 mL beaker, distilled water, acetone, ethanol C. Procedure1. pH Test: 1) Measure 10mL of distilled water in a 50 mL beaker 2) Measure .1g of unknown chemical 3) Pour unknown chemical into water and stir 4) Using a pH strip, dip the strip into the solution and compare to pH strip container to determine pH range 5) Using a pH indicator, place the indicator into the solution to determine the pH 2. Flame Test: 1) Obtain the remaining amount of unknown chemical in a 50 mL beaker 2) Measure 10 mL of distilled water into a second 50 mL beaker 3) Dip the wire loop in the water then into the unknown sample to have the chemical stick to the wire loop. 4) Place the wire loop into the blue part of the flame 5) Observe the color of the flame 3. Solubility Test: 1) Measure 20 mL of distilled water in a 50 mL beaker 2) Measure 20 mL of ethanol in a second 50 mL beaker 3) Measure 20 mL of acetone in a third 50 mL beaker 4) Pour .1 g of unknown sample into each beaker 5) Stir and observe if the chemical is soluble or insoluble.

D. Week 2 Methods1. For week two, a pH test, flame test, and solubility test was performed on the final three chemicals from the previous week to then narrow it down to one chemical (which was Ammonium Chloride) to determine what the unknown sample was.

2. After reaching a final chemical that matched the unknown sample, a gravimetric analysis using Silver Nitrate was performed to confirm if Ammonium Chloride was actually the identity of the unknown chemical sample. E. Materials1. Magnesium Sulfate: 1) pH Test: .1 g of Magnesium Sulfate, 1x 50 mL beaker, distilled water, pH strips, pH indicator 2) Flame Test: .1g of Magnesium Sulfate, 1x 50 mL beaker, distilled water wire loop, Bunsen burner 3) Solubility test: .1g of Magnesium Sulfate, 1x 50 mL beaker, distilled water 2. Ammonium Sulfate: 1) pH Test: .1 g of Ammonium Sulfate,1x 50 mL beaker, distilled water, pH strips, pH indicator 2) Flame Test: .1g Ammonium Sulfate, 1x 50 mL beaker, distilled water wire loop, Bunsen burner 3) Solubility test: .1g of Ammonium Sulfate, 1x 50 mL beaker, distilled water 3. Ammonium Chloride: 1) pH Test: .1 g of Ammonium Chloride, 50 mL beaker, distilled water, pH strips, pH indicator 2) Flame Test: Wire loop, distilled water, Bunsen burner, beaker, Ammonium Chloride 3) Solubility test: .1g of Ammonium Chloride, 50 mL beaker, distilled water 4. Gravimetric Analysis, using Ammonium Chloride & Unknown Chemical: 1) .1g of unknown chemical, .1g of Ammonium Chloride, 10 mL of Silver Nitrate, 2x 250 mL Erlenmeyer flask distilled water, funnel, filter paper, glass dish F. Procedure*This test was performed three times, each time with a different chemical from the final three* 1. pH Test: 1) Measure 10mL of distilled water in a 50 mL beaker 2) measure .1g of chemical being tested

3) Pour chemical being tested into water and stir 4) Using a pH strip, dip the strip into the solution and compare to pH strip container to determine pH range 5) Using a pH indicator, place the indicator into the solution to determine the pH 2. Flame Test: 1) Obtain small amount of chemical being tested in a 50 mL beaker 2) Measure 10 mL of distilled water into a seond 50 mL beaker 3) Dip the wire loop in the water then into the chemical being tested to have the chemical stick to the wire loop. 4) Place the wire loop into the blue part of the flame 5) Observe the color of the flame 3. Solubility Test: 1) Measure 20 mL of distilled water in a 50 mL beaker 2) Measure 20 mL of ethanol in a second 50 mL beaker 3) Measure 20 mL of acetone in a third 50 mL beaker 4) Pour .1 g of chemical being tested into each beaker 5) Stir and observe if the chemical is soluble or insoluble. 4. Gravimetric Analysis: *This test was performed twice, once with Ammonium Chloride and once with the unknown sample* 1) Measure .1 g of unknown sample A on a glass dish 2) Measure 100 mL of distilled water into an Erlenmeyer flask 3) Mix the sample with the water and stir 4) Add 10 mL of Silver Nitrate to solution and stir to allow precipitation 5) Obtain a second Erlenmeyer flask 6) Place funnel with filter paper into flask and slowly pour solution with the precipitate into the new flask 7) Once filtered, take filter paper and place it in the oven, for 15-20 mins, for the precipitate to dry 8) Weigh the precipitate and record the mass

9) Repeat steps 1-9, but instead of using the unknown sample, use Ammonium Chloride 10) Once the precipitate is weighed compare the weights of the two precipitates to confirm identity of the unknown chemical. G. Safety1. Magnesium Sulfate: 1) Hazardous in case of ingestion. Slightly hazardous in case of skin contact (irritant), of eye contact (irritant), of inhalation. Safety glasses. Lab coat. Dust respirator. Be sure to use an approved/certified respirator or equivalent. Gloves..1 2. Ammonium Sulfate: 1) Hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion (if ingested Do NOT induce vomiting unless directed to do so by medical personnel), of inhalation. Splash goggles. Lab coat. Dust respirator. Be sure to use an approved/certified respirator or equivalent. Gloves. .2 3. Ammonium Chloride: 1) Hazardous in case of eye contact (irritant). Slightly hazardous in case of skin contact (irritant, sensitizer), of ingestion, of inhalation. Splash goggles. Lab coat. Dust respirator. Be sure to use an approved/certified respirator or equivalent. Gloves.3 4. Silver Nitrate: 2) Very hazardous in case of skin contact (irritant), of ingestion. Hazardous in case of skin contact (permeator), of eye contact (irritant), of inhalation. Slightly hazardous in case of skin contact (corrosive). The amount of tissue damage depends on length of contact. Eye contact can result in corneal damage or blindness. Skin contact can produce inflammation and blistering. Inhalation of dust will produce irritation to gastro-intestinal or respiratory tract, characterized by burning, sneezing and coughing. Severe over-exposure can produce lung damage, choking, unconsciousness or death. Prolonged exposure may result in skin burns and ulcerations. Over-exposure by inhalation may cause respiratory irritation. Splash goggles. Synthetic apron. Vapor and dust respirator. Be sure to use an approved/certified respirator or equivalent. Gloves.4

III.

RESULTS: A. Week 1 Results1. After performing a pH test, flame test, and solubility test on the unknown chemical, this is what resulted:

Chemical(s)

pH

Flame

Solubility

Unknown Sample A

Strip: Weakly Acidic Indicator: 6

Light Green

Water: Soluble Acetone: Insoluble Ethanol: Insoluble

2. After comparing these traits to the 11 possible chemicals only three chemicals matched, which were Magnesium Sulfate, Ammonium Sulfate, and Ammonium Chloride. B. Week 2 Results1. After performing a pH test, flame test, and solubility test on the final three chemicals, this is what resulted: Chemical(s)

pH

Flame

Solubility

Ammonium Chloride

Strip: Weakly Acidic/Neutral Indicator: 6.5

Light green/blue

Ammonium Sulfate

Strip: Weakly Acidic/Neutral Indicator: 6.7

Light green

Magnesium Sulfate

Strip: N/A Indicator: N/A

Doesn’t burn

Water: Soluble Acetone: Insoluble Ethanol: Insoluble Water: Soluble Acetone: Insoluble Ethanol: Partially Soluble Water: N/A Acetone: N/A Ethanol: N/A

2. Magnesium Sulfate was immediately eliminated as one of the choices because it did not burn in the flame test and Ammonium Sulfate was also eliminated because the pH was close to neutral which was too far from the known chemical pH. This left Ammonium Chloride as the final identity for the unknown chemical. IV.

DISCUSSION:

During week 1, the characteristics of the unknown chemical were tested using a pH test (with both the strips and the indicator to make sure the result was accurate), a flame test, and a

solubility test (using water, alcohol, and ethanol). The results were as followed; the pH was weakly acidic and 6, the flame color was light green, and the chemical was soluble in water but insoluble in alcohol and ethanol. These tests were selected to be done because then both physical and chemical characteristics of the unknown chemical can be recorded. Also, these tests were quick to do and could immediately eliminate those chemical choices that didn’t match. After recording the final results of the unknown, the characteristics of the eleven other possible choices were researched and compared. Those that didn’t match were eliminated and the selection was narrowed down to three possible choices, Magnesium Sulfate, Ammonium Chloride, and Ammonium Sulfate. During week 2, the characteristics of the three final choices were tested used the same tests as week one. The results were as followed; for Ammonium Chloride, the pH was weakly acidic and 6.5, the flame color was light green/blue, and the solution was soluble in water, and partially soluble in ethanol and alcohol. For Ammonium Sulfate, the pH was weakly acidic and 6.7, the flame color was light green, and the solution was soluble in water, partially soluble in ethanol, and insoluble in alcohol. Lastly for Magnesium Sulfate, the only test performed was the flame test because the chemical didn’t burn and could be safely eliminated from the selection. Between the final two chemical choices of Ammonium Sulfate and Ammonium Chloride, Ammonium Sulfate was eliminated because the pH was close to neutral and didn’t match the unknown result of weakly acidic/6. With the final choice of Ammonium Chloride, a gravimetric analysis was done, with Silver Nitrate, and compared to the analysis of the unknown. In the end, both tests ended up not having a precipitate, which confirms that the unknown chemical was indeed Ammonium Chloride. A few errors occurred during the experiment. The first one was after performing the gravimetric analysis, when the solutions were filtered out through the filter paper, there was little to no precipitate that could actually be dried, measured and compared. To try to fix this, the 50 mL beaker with the solution was placed in a 150 mL filled with ice to try to slightly change the state of the solution. However, that didn’t change the final results. Another error that occurred was during the flame test, when the chemical was burned on the wire loop the flame turned orange which was recorded as the color of the chemical when burned. However, the wire loop material itself made the flame change to orange. This mistake mixed up the elimination of a few

of the chemical choices, and the test had to be performed again. There are a few changes that would be done to the experiment to make it go smoother and conclude with more accurate results. The first would be to keep stirring the beaker, when performing a solubility test, to see if the reaction was maybe partially soluble or truly insoluble. Something else that would change is to use a different utensil to burn the chemical, when performing the flame test, because the wire loop when placed in the flame produced an orange color, which was recorded as the final color of the chemical being tested. V.

CONCLUSION:

The original hypothesis for this experiment was to be able to identify an unknown chemical by comparing its chemical and physical characteristics to the characteristics of eleven other possible chemical choices. By eliminating the choices that didn’t match, the chemical selection was narrowed down from eleven to one final chemical. The hypothesis was proven correct, by performing a variety of tests the unknown chemical was identified as Ammonium Chloride. As mentioned in the discussion, a major error occurred when the gravimetric analysis was performed. When the solutions were filtered out, there was little to no precipitate that could actually be measured and compared. Also, because there was no precipitate available, a percent error could not be calculated. VI.

RESEARCH CONNECTION:

At Queen University’s Belfast, chemists have developed a new method for identifying and screening substances contained in “legal highs”. Legal highs are substances that are used like illegal drugs, but are called legal because when they were first produced they were not covered by the existing drug laws. This new tactic combines the screening of known drugs with an indepth analysis of new compounds. The screening operates by identifying the characteristic vibrations of the bonds within the samples by focusing a laser on the sample and measuring the energy of light scattering from it. The vibrations are chemical signatures of the compounds, so when they have been recorded, they can be searched against the 'library' of known compounds. They are then either identified as known compounds or marked as new variants which can then be taken for further analysis in the laboratory. 5 The main findings from this study is that 75 % of 200+ samples taken in by the police could immediately be identified. The motivation for this study was the public health of the communities. This new approach allows companies to quickly

identify any matter with legal highs, thus promoting more public health messages to be sent out to the communities. Along with the safety of the public, this approach allows agencies to know which drugs are currently be used and even helps speed up related criminal prosecutions. This study relates to the experiment performed because they both comprise of identifying unknown substances and comparing the findings to already known substances. VII. 1

REFERENCES:

Magnesium sulfate anhydrous MSDS https://www.sciencelab.com/msds.php?msdsId=9927218

(accessed Feb 27, 2017). 2

Ammonium sulfate MSDS https://www.sciencelab.com/msds.php?msdsId=9927078(accessed

Feb 27, 2017). 3

Ammonium chloride MSDS https://www.sciencelab.com/msds.php?msdsId=9927431

(accessed Feb 27, 2017). 4

Silver nitrate MSDS http://www.sciencelab.com/msds.php?msdsId=9927411 (accessed Feb 27,

2017). 5

Bell, S; Brown, S. Royal Society of Chemistry's. 2011, 47 (3), 460–461.

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Ratliff, J; Chem I Powerpoint on Precipitation Reactions (Chapter 4)

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Ratliff, J; Chem I Powerpoint on Ionic Compounds and Solubility (Chapter)...